1. Field of the Invention
The present invention relates to a power semiconductor module device, especially to a resin encapsulated power semiconductor module device that realizes effective thermal radiation, and a production method thereof.
2. Background Art
Conventionally, power semiconductor module devices have been used for electronic devices such as inverters, converters, servos, and the like. FIG. 5 shows a cross-sectional view of a conventional power semiconductor module device. As shown in FIG. 5, the power semiconductor module device comprises a circuit board with metal plates 103a and 103b bonded to both sides of a ceramic material 102, the circuit board being fixed on a metal base plate 101 using solder 104a. And a semiconductor element 106 is fixed on a surface side metal plate 103a of the aforementioned circuit board using solder 104b. 
An outer case 107 having an insert-molded outlet terminal 108 is attached to the metal base plate 101 such that it is erected on the metal plate 101. Electric connection between the semiconductor element 106 and the outlet terminal 108 is performed via an aluminum bonding wire 109. A resin material 110, such as silicon gel, is used to fill in an internal space delimited by the outer case 107.
In the aforementioned electronic devices such as inverters, converters, servos, and the like, regarding semiconductor elements capable of use for various types of power systems that are usually mounted, such as diodes, transistors, IGBT (Insulated Gate Bipolar Transistor), MOSFET, or the like, ceramic materials are selected through which insulation and thermal conductivity functions of the circuit board are performed depending on each heat release value. In medium to high capacity devices that have high heat release values, aluminum nitride ceramics are mainly used. In small to medium capacity devices, alumina ceramics are used.
In particular, as the demand for the reduction of environmental burdens has been increasing, the application of power semiconductor mounted devices to automobiles, such as hybrid cars, has rapidly made progress. Conventionally, power devices applied to automobile driving systems have high heat release values, so that circuit boards employing aluminum nitride in an insulated layer have been used.
With the progress of material development technologies, silicon nitride having superior strength characteristics has attracted attention, and applied research has been in progress regarding silicon nitride having both high strength and high thermal conductivity to be used for silicon nitride circuit boards as a material substitutable for aluminum nitride circuit boards (see Patent Documents 1 to 3, for example).
Patent Document 1: JP Patent Publication (Kokai) No. 9-162325 A (1997)
Patent Document 2: JP Patent Publication (Kokai) No. 10-190176 A (1998)
Patent Document 3: JP Patent Publication (Kokai) No. 2002-84046 A